1. Field of the Invention
This invention relates generally to web handling mechanisms, and more specifically to a web slack box having a plurality of sections.
2. Description of the Prior Art
It is known in the prior art to provide slack boxes for storing web material at the feed and take-off ends of a continuously operating machine such as a photographic film processing device. This permits intermittently stopping film transport into or out of the device for short periods of time for some purpose such as inspection, splicing, or the like without affecting the continuous operation of the processing device. One type of slack box for such a machine is shown in German Pat. No. 138,821 comprising one or more solution-filled tanks into which the film is freely randomly fed in serpentine or looped fashion. Such a slack box is not usable in applications in which a dry web is stored or accumulated. Another slack box of this general type receives a freely falling dry web in serpentine or looped fashion, but it is incapable of accumulating a sufficient length of film without crushing the bottom or lower loops of web due to the weight of the upper web loops or convolutions. Another type of slack box, having a rotatable accumulator, is disclosed in U.S. Pat. No. 3,693,859. The slack box comprises a rotatable hub and a plurality of radially extending partitions rotatable therewith and cooperating with a pair of spaced side plates or discs to form a plurality of angularly spaced compartments open at the periphery. The film is fed by a film-feeding mechanism into each of the film compartments in succession as the hub and partitions are rotated by a hub drive mechanism past the film feeding mechanism. The rate of film feed into each compartment and the rotational speed of the hub are selected such that each compartment is substantially filled with film convolutions such as coils and loops of film before the film enters the next succeeding compartment.
Another well-known type of slack box comprises a film supporting elevator mechanism for normally accumulating the film on rollers rotatably mounted on upper and lower spaced apart, parallel shafts. The upper shaft is fixed, and the lower shaft and rollers form a part of a vertically, reciprocally movable elevator mechanism. Accordingly, when the film feed into the processing device is stopped to permit a splicing operation or the like, the elevator mechanism begins to move upwardly as the film continues to be withdrawn from the slack box, and when it reaches a predetermined height, a switch is activated by any suitable means for enabling or actuating the film-feeding mechanism. Since the film is fed into the slack box at a faster rate than it is withdrawn therefrom, the elevator mechanism will then move downwardly as it accumulates film, and when it reaches a predetermined point where sufficient film has been accumulated, it will actuate another switch disabling or deactuating the film-feeding mechanism. Although the elevator slack box operates in a satisfactory manner, it is of relatively complicated construction comprising many parts that greatly increases problems of assembly, operability and repair. Accordingly, such slack boxes are expensive to manufacture, and in addition take up a considerable amount of space. Furthermore, in view of the larger number of rollers and loops involved, the force required to pull the film through the slack box is relatively high.
Still another known type of slack box is disclosed in U.S. Pat. Nos. 2,855,196 and 2,889,491, and in an article entitled "Operational Experience with Seac" by Ernest F. Ainsworth in "The Review of Input and Output Equipment Used in Computing Systems" published by AIEE, Mar. 1953. In this slack box, one or both of the walls of the box is provided with laterally protruding fixed projections extending partially into the box chamber for releasably catching upper web convolutions, thereby preventing crushing of the bottom web convolutions. A disadvantage of this type of slack box is that the projections are fixed and the web convolutions have to be pulled past the projections as the web is fed from the slack box. This results in increasing the inertia of the system and possible web damage due to web deformation or creasing.